Apparatus and method for preheating of air and the like by conduction



Feb. 24,1942. o, L EY ET AL 2,273,902

APPM'UVIUS AND METHOD FOR PREHEATING OF AIR AND THE LIKE BY CONDUCTION Filed Sept. 30, 1940 2 Sheets-Sheet l V INVENTORS OLIVER MALLEYX: HEBBEEIA..BEEE.

Feb. 24, 1942. 2,273,902

APPARATUS AND METHOD FOR PREHEATING OF AIR AND THE LIKE BY CONDUCTION O. SMALLEY ET AL Filed Sept. 30, 1940 2 Sheets-Sheet 2 0111/1311? SMALZZEEERS BY IiERBERIA.RE 6E.

Patented Feb. 24, 1942 APPARATUS AND METHOD Foa PREHEAT- me or Am AND THE LIKE BY CONDUCTION Oliver Smalley, Pittsburgh, Pa., and Herbert A. Reece, Cleveland Heights, Ohio, assignors to Meehanite Metal Corporation, a corporation of Tennessee Application September 30, 1940, Serial No. 359,018

18 Claims.

- Our invention relates to furnaces and more particularly to metallurgical furnaces such as cupolas and the like, and to the operation of the same.

air supply for a furnace.

- lar device.

' placement.

had no provision to assure a uniform pre-heating of the air supply for the furnace by modifying the air flow to substantially equalize the air flow at the location of heating and simultaneously heating the air flowing at all radial out ward distances from the said annular shell or The present invention provides for the emcient By simultaneously distributing the heat and dis- It is an object of the present invention to ob- Another object of the invention is the provision Another object is the provision for theobtain- Another object is the provision for obtaining Another object is the provision of improved Another object is the provision for the conduc- Another object is animproved structure for,

And a still further object is the provision of The present invention is related in general 5 subject matter to the disclosures of our co-pendring. ing applications, Ser. No. 338,468 and Ser. No.

338,514, both filed June 3, 1940, and is directed and uniform heatingof the air flowing through to similar and other problems of pre-heating the a wind box by transferring .heat by conduction l0 radially outwardly from the interior of the fur- The invention disclosed herein is directed to nace through the wall ofthe furnace into the the pre-heating of air supplied to a metallurgical wind box, the heat being distributed at all radial or other furnace for the promotion of combusdistances within the wind box, and by distributtion therein. In this discussion and description ing the flow of airuniformly in the wind box in the operation and structure of a cupola for the exchange'relationship with the conducted heat. remelting of metal is referred to but it is to be understood that our invention includes the structributing the air flow in the manner here deture and operation of other furnaces and similar scribed an emcient and improved pre-heating of devices wherein'a blast of air or other gases is the air blast is obtained and the pre-heated air supplied through a plurality of tuyeres or like 2 is supplied uniformly to each of a plurality of openings to the interior of the furnace or simituyeres.-

'Ihepresent invention utilizes the heat generviate the limitations, defects and disadvantages ated within the cupola for pre-heating the air of systems in prior use. delivered through the cupola tuyres to the interior of the cupola. During operation of the of an improved system of pre-heating the air cupola the coke or other similar fuel charged I supplied to a cupola affording results and preinto the cupola burns and generates a large senting advantages not heretofore known or obamount of heat within the shaft of the cupola. tainable. I The heat thus generated is usually carried upwardly in the cupola shaft by the gases in the ing of the maximum amount of heat from the cupola and is lost to atmosphere at'the top of hot gases of the cupola in pre-heating the air the cupola. As the wall of the cupola is genersupplied to the cupola. ally formed of heat resisting or refractory material such as flre bricks, there is relatively little a more uniform heating of the air supplied to heat loss through the wall of the cupola. This a cupola. wall is generally composed of a relatively thin Another object is the provision for a distribuouter shell of iron and a relatively thick lining tion of air flow in a system to obtain a uniform of inter-laid fire bricks forming the effective heating of the air supplied to a plurality of cubody of the cupola, the outer shell providing a pola tuyres. bond to retain the fire bricks against radial disa apparatus for the utilization of heat generated In pre-heating systems prior to the present inby a cupola for the efllcient. pre-heating of the vention there has been an attempt to utilize some air supplied to the tuyres of the cupola. of the heat generated within the cupola by eliminating the fire brick wall at a location adjation of heat generated by a cupola for the precent to the air in conduits outside of the cupola heating of the air supply for the cupola at a locommunicating with the tuyeres and substituting cation exterior of the cupola. for this fire brick wall an annular shell or ring of heat conducting material such as iron. In, and method of, pre-heating the air supply of a these prior structures, however, the air next adfurnace by conduction. Jacent to this annular shell or ring was heated more than the air flowing at a radially outward conduction apparatus and method of producing distance. Such prior structures as described here results not heretofore obtainable by conduction.

Other objects and a fuller understanding of our invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which: 7

Figure 1 is a cross-sectional view taken lengthwise of a cupola and wind box embodying our invention and is a view looking in the direction of the arrows i-I of Figure 2;

Figure 2 is a transverse cross-sectional view taken through the line 22 of Figure 1;

Figure 3 is an enlarged perspective view of one of the conduction members utilized in the apparatus shown in Figures 1 and 2;

Figure 4 is a view somewhat similar to that of Figure 2 but shows a modified form of conduction members mounted in the apparatus;

Figure 5 is an enlarged perspective view of one of the conduction members of modified form utilized in the apparatus shown in Figure 4;

Figure 6 is another cross-sectional view taken lengthwise of a cupola and wind box in the direction of the arrows 8-6 of Figure 7 and illustrates still another modified form of conduction members mounted in the apparatus;

Figure 7 is a transverse cross-sectional view taken through the line 17 of Figure 6;

Figure 8 is an enlarged perspective view of one of the conduction members utilized in the apparatus shown in Figures 6 and 7;

Figure 9 is a view somewhat similar to that of Figure 7 but shows a further modification of the conduction members shown in Figures 6, 7 and 8; and

Figure 10 is an enlarged perspective view of p one of the conduction members utilized in the apy paratus shown in Figure 9.

, Inasmuch as the invention disclosed herein is directed particularly to the wind box, the portion of the cupola adjacent thereto and the heating arrangement associated therewith, it has not been considered necessary to show all parts of the cupola nor all views thereof in the several figures. The portions of the cupola and wind box not shown, however, may be considered as having the usual and well known form. Also, for purposes of simplicity in illustration, the usual tap hole and slag hole are .not shown. It has also been considered unnecessary to illustrate such other openings as a clean-out door, breast arch or drop-bottom door. The cupola to which the invention is associated and which is described herein may be considered, however, as having all of the parts necessary for the usual operation of the same.

As shown in the several views of the drawings, the cupola body or shell 2| is in the form of a cylindrical shaft, the inner wall of the cupola body 2| being lined by the fire brick lining 24.

The shell 2| and lining 24 are mounted upon a usual bottom plate and thereby form the enclosed shaft or stack of the cupola. Suitable supports are provided to form a base for the support of the cupola.

' The fire brick lining 24 is comprised of a plurality of over-laid bricks made of suitable re- 'fractory material, the crevices and inner face of the brick wall being daubed with suitable refractory plastic material'hardened in place. The refractory lining 24 is relatively thick and confines the contents of the cupola and at the same time provides an insulation confining the-great heat generated within the furnace. The shell 2| is relatively thin and being made of iron or other relatively strong material forms a bond around the lining 24 to hold the same against radial displacement.

A wind box 22 of cylindrical shape is mounted upon the cupola shell 2| by welding or other suitable means. The outer wall of the cupola body forms one of the enclosing walls of the wind box and there istherefore a common wall between the cupola and the wind box. The wind box 22 forms an enclosed jacket surrounding the cupola body 2| in such a way that air introduced into the wind box may circulate entirely around the cupola body.

An inlet conduit 23 is in communication with 'an air blower or other source ofan air blast (not shown) and the inlet conduit 23 is connected to the upper portion of 'the wind box 22 so as to afiord communication between the air blower and the inlet opening 25 of the wind box 22.

In the cupola illustrated there are six tuyeres extending through the wall and lining of the cupola body 2| to establish communication between the interior of the shaft of the cupola and the lower portion of the wind box 22. All six tuyeres 30, 3|, 32, 33, 34 and 35 are shown in dotted lines in the transverse cross-sectional views of the drawings and three of the tuyres 30, 3| and 32 as seen from the inside of the shaft of the cupola are illustrated in the cross-sectional views taken lengthwise of the cupola. These six tuyres are of substantially equal size and are uniformly spaced around the periphery of the cupola. The-tuyeres enter the cupola body at a low level in the cupola and communicate with the lower portion of the wind box.

With reference to Figures 1, 2 and 3 of the drawings in which a first form of the invention is illustrated, a plurality of conduction members 36 comprising fiat plates of copper or other suitable material of high heat conductivity are shown mounted to extend radially of the cupola. The inner radial end of each member 36 is embedded in the refractory lining 24. The inside edge of the conduction members are bent at right angles to form a flange 31. This flange 31 is positioned close to, but slightly within, the inner wall surface of the lining and is thus in proximity to the heat generated within the cupola but is not in direct contact with the hot gases and contents of the cupola and is thus in heat exchange relationship with the interior of the furnace and at the same time is protected from being burned or melted. The copper plate if extended into direct contact with the interior of the furnace would be subject to burning or melting.

The members 36 extend radially outward, through open spaces or slits provided in the shell 2|, across the interior of the wind box to the outer wall of the windbox and thus form a series of spaced vertical walls dividing the wind box into a series of vertical air passageways disposed around the circumferential extent of the wind box.

The air blast enters the wind box 22 from the inlet conduit 23 in a tangential direction relative to the annular wind box. If th air blast is permitted to circulate at will around in the wind box there will be an unequal flow of air in different parts of the wind box. Herbert A. Reece United States Letters Patent No. 2,188,920 issued February 6, 1940; No. 2.197,- 947 issued April 23, 1940; No. 2,197,948 issued April 23, 1940; and No. 2,197,949 issued April 23, 1940, the air blast will flow in currents of unequal velocity and enter the several tuyeres at unequal As pointed out in the suppliedby the plates.

velocity in the absence ofpropercontrol means in the wind box for modifying the flow of air.

' In the present structure, the air blast circa-,- iating around the wind box is broken up or diverted by the vertical plates and forced to flow downwardly in a longitudinal direction relative to the wind box before entering the tuyeres. The uniform distribution of the plates 38 around the circumferential extent of the wind box provides for a substantially uniform flow of air through the wind box to the, tuyeres. The provision for equalizing the flow of air throughout the cross-sectional area of the wind box contributes I to the uniform heating of the air throughout the wind box and the delivery of uniformly heated air to the plurality of'tuyeres. Heat generated within the cupola is received by the inner radial edge portions of the plates 36, and particularly by the flanges 31 formed thereon, and the heat is carried by conduction radially outward through the portion of the plates embedded in the wall to the portion of the plate extending between the walls of the wind box. By reason of the high conductivity of the plates of copper or similar material this transfer of heat from the cupola to the wind box is relatively rapid and the temperature of the outer radial extremity of the plates is maintained at substantially as high av degree of heat as the temperature of the plates next adjacent to'the wall of the cupola. The

' box.

plates therefore form a heater capable of delivering heat at substantially the same degree of temperature throughout the cross-sectional area of the wind box. v

Air flowing substantially the same at all locations in the cross-sectional area of the wind box at the. heater is heated uniformly by the heat As the air flows adiacenttofboth of the opposite sides of the plates the 'air'will be equally heated on said opposite sides. The air flows adjacent to the same area to the interior of the cupola and is protected from direct contact with the interior of the furnace. I

The outer radial portion 39 of the modified conduction member is waved or corrugated in a direction longitudinal of the cupola and wind box. This deformed shape of the plate within the wind box provides a greater heating surface for effective transfer of heat to the air in the wind box. Other variations of form may be'devised for the effective heating of the air within the wind box in accordance with the teachings of the present disclosure.

In Figures 6, '7 and 8 of the drawings there is illustrated a modified form of conduction members for transferring heat from the interior of the cupola to the air passing through the wind box. Each of these modified conduction members comprises a vertical plate 4| having a plurality of fins 43 extending out from the opposite sides of the portion of the plate positioned in the wind The fins 43 are curved somewhat to be better accommodated in the annularinterlor of the wind box and to provide for more uniform spacing of the several fins in respect to fins of adjacent conduction members. The outer ends of the fins 43 are in relatively close juxtaposition to the outer ends of fins of the next adjacent conduction members. By the arrangement illustrated in Figures 6 and '1 it is seen that the conduction members are brought in close proximity to all ofthe air passing through the wind box. There is a finer subdivision of the heat transferred-by conduction through the metal of the conductionmembers and this heat is then brought into more intimate contact with the air to be heated by means of the finned conduction members.

of heating surface throughout its downward-passage through the wind box and is therefore heated in substantially the same degree. As the plates are equidistant from a plane passing through the tuyeres the air travels substantially the same distance from the plates to each of the plurality of tuyeres, is subject to the same heat exchange conditions, and is delivered to all. the tuyeres at substantially uniform temperature.

The plates may be spaced apart, and the number thereof added or subtracted, in accordance with the size and shape of the cupola and wind box, it being desired that there be s'ufllciently a close spacing of the plates that all of the'air should flow in relatively close proximity to the,

heating surfaces of the plates to be uniformly heated thereby. The spacing and number of plates shown in the drawings have been selected for the purposes of simplicity of illustration and of demonstration of the principles of the invention; It is to. be understood that the drawings are only by way of example and that the necessary changes required for the particular installation involved are included within the meanin of our disclosure.

In Figures 4 and 5 we illustrate a modification in theform of the plates or conduction members.

' The modified conduction member has an inner radial portion 38 that is flat and which is embedded in the wall of the cupola. The inner extreme end of the plate has a T-shaped flange 40 which provides a larger mass for the reception offthe heat generated in the cupola. This flange 40 is positioned in close heating proximity The inner end of each vertical plate 4| has a T-sh aped head 41 which is also slightly curved to better complement the annular shape of the lining 24 of the cupola wall. The heads 42 are spaced somewhat from th inner surface of the cupola shaft and covered by refractory materialto prevent burning or melting of the head by the hot gases in the furnace but are spaced sufficiently close to the interior of the shaft to receive a considerable amount of heat.

The heat received by the heads 42 is conducted through the metal, preferably copper, radially V outwardly through the vertical plates ll embedded in the cupola wall to the interior of the wind box. The portion of the plates 4| in the wind box and the fins extending therefrom thereby receive heat by conduction from the interior of the furnace. Air passing in close proximity to the uniformly distributed plates and fins is preheated thereby and is supplied to the tuyer'es in uniformly heated condition. The fins by further sub-dividing the area of the wind box aid 1 in breaking up tangential fiow of air in the wind box and in uniformly distributing the airin its flow from the wind box inlet to the outlets.

The conduction members having the fins extending therefrom have a relatively large amount of heating surface and thus provide an efficient means of rapid transfer of heat from-the metal of the conduction inembers to the air. The radially outward fins being longer than the radially inward fins provide for an adequate amount of heating surface where the volume of air to be heated is greatest. The metal, preferably copper. being a rapid conductor of heat supplies heat substantially uniformly to all portions of the conduction members and the air is uniformly heated thereby.

In Figures 9 and 10 there is illustrated a modifled form of the finned conduction members shown in Figures 6, 7 and 8, In the modified form of conduction members illustrated in Figures 9 and 10, the vertical plate at has a plurality of fins 66 extending out at right angles thereto. The manufacture of conduction members with fins at right angles is simpler and more In wind boxes wherein th annueconomical. lar curve of the wind box is relatively small in comparison with the length of the fins the conduction members with straight fins will be found satisfactory. As seen in Figure 9, the fins 46 substantially follow the contour of the annular wind box.

The inner end of the vertical plate 44 shown in Figures 9 and 10 is further modified from that previously described in that a T-shaped head 45 e a-races ing through said 'outer' wall and inwardly of said The head 45 is welded or otherwise integrally joined with the plate 44 which is composed'of a metal of high conductivity such as copper and which need not be as resistant to burningand melting as-must be the head 45.

The heads 45 are slightly curved 'and their edges abut with. those of the-adjacent heads. In this manner a segmental :metallic cylinder is formed at the inner surface of the cupola shaft and a considerable portion of the heat generated in the cupola is thus received for conduction outwardly through the conductionmembers.

Although we havedescribed our invention with a certain degree of particularity, it is to be understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts'may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

We claim:

1. In a furnace having a wind box positioned adjacent to the wall of the furnace for supplying a blast of air to a plurality of tuyres, said wall comprising a shell and refractory lining, said wind box having an inlet adapted to communicate with a source of an air blast and having outlets in communication with said tuyeres, a plurality of heat-conducting members disposed within said wind box and substantially uniformly distributed around said furnace for heating the air blast passing through the wind box from the inlet to the outlets, said heat-conducting members extending through said shell and into within the furnace.

2. In a furnace having a wind box positioned adjacent to the outer wall of the furnace for supplying air to a plurality of tuyres, said outer wall embracing an inner wall of refractory matesaid refractory lining to receive heat generated rial, a plurality of heat-conducting members extending outwardly from the said furnace wall into said windbox to heat the air passing ,therenew for supplying an air disposed in said posed in heat inner wall to receive heat generated within the furnace. 4

3. In a furnace having a wind box positioned adjacent to the wall of the furnace for supplying a blast of air to a plurality of tuyeres, said wall comprising a shell portion and a refractory per-a tion, the wind'box having an inlet adapted to communicate with a source of an air blast and having outlets .in communication with said tuyres,.a plurality of longitudinal conduction members disposed radially of the furnace in said wind box and extending longitudinally of the wind box substantially perpendicular to parallel planes passing through the inlet and through the outlets, said conduction members extending through said shell portion and into the refractory portion of said furnace w'all toward the interior of the furnace in proximity to heat generated within "the furnace, the heat conducted by said conduction members from said furnace to the wind box heating the air blast passing through the wind box longitudinally of, and intermediate of, said conduction members.

4. In a furnace having a wind box positioned adjacent to and encircling, the wall of the furblast to a plurality of tuyres, said wall having a shell encircling a refractory. lining, a pluralltyof metallic plates wind box substantially radially of the furnace, the said plates having inner radial portions extended through said shell and embedded in the refractory lining of said wall and disposed in heat exchange relationship with theinterior of the furnace'and'having outer radial portions spaced from each other and disv exchange relationship with the air blast passing through the wind box, said air, blast being pre-heated in said wind box by the heat generated in the interior of the furnace and conducted'by said metallic plates.

5. Ina furnace having awind box positioned around the body of the furnace for supplying blown air through a plurality of tuyeres to the interior of the furnace for the promotion of to communicate with a source of .said blown air and having outlets in communication-with said I tuyres, a heater mounted within said wind box intermediate the said inlet and said outlets in the path of the flow of air through the wind box, said heater having a plurality of passageways extending therethrough for the flow of air from the portion of the wind box adjacent said inlet to the portion of the wind box adjacent said outlets, said passageways being substantially uniformly distributed in the wind box around said furnace, said heater having-heat conducting portions extending through said metal shell and into the refractory lining of said common wall to heat exchange position relative to the interior of the furnace, said heat conducting portions conducting heat generated within the furnace to said heater for pro-heating the air in said wind box.

6. A heater for pre-heating the air blast passing through a wind box from an inlet to a plurality of tuyres of a furnace in which heat is generated, said furnace having a refractory wall embraced by an outer shell, said heater having a plurality of spaced heating portions distributed around the wind box in the path of the air blast therein for heating said air blast, the said heater having heat conducting portions in thermal con.

nection with said heating portions extended through the outer shell into said refractory wall and inwardly toward the interior of the furnace in heat exchange relationship with the heat genthe furnace, heat received from the furnace bein conducted by said plates into the wind box to heat said air.

erated' in the furnace, said heat conducting porcommon wall and radiating outw'ardlythrough said shell from said common wall into heat exchange relationship with the air in said wind box, the fins radiating inwardly from said shell toward the interior of the furnace into heat exchange relationship with the heat in said furnace, said fins conducting heat radially outwardly from the furnace into'the wind box for heating the air therein.

8. In a furnace having a wind box positioned nace having a shell surrounding a refractory,' a plurality of metal plates spaced uniformly-around the wind box and extending radially outwardly from the furnace into the wind box, said plates extending inwardly of the furnace through said shell into said refractory and into proximity to the heat in the furnace, the plates transferring heat by conduction from the furnace to the wind box.

9. In a furnace having a wind box positioned adjacent'to, and encircling, the furnace, the wind box and furnace having a common wall comprised of a shell and a refractory, a plurality of metal plates extended through the shell and embedded in the refractory of said common wall and extending radially outwardly from a position proximate to the interior of the furnace to a position within the wind box, said plates conducting heat from the interior of the furnace through the shell of said wall into the wind box.

10. In a furnace having a wind box positioned adjacent to, and encircling, the furnace, the wind box and furnace having a common wall comprised of ashell and a refractory, a plurality of metal plates uniformly distributed around the windbox and disposed vertically in the wind box 12. In a furnace having a wind box positioned adjacent to, and encircling, the furnace for supplying an air blast to a plurality of tuyres, the

wind box having an inlet adapted'to communicate with a source of an air blastand having outlets in communication with said tuyres, said furnace having a wall comprised of a shell and a refractory, a plurality I of members having heating and guiding surfaces disposed in, and distributed at intervals around, said wind box, said surfaces guiding said air blast longitudinally of the wind box from the portion adjacent the inlet to the portion adjacent said outlets and simultaneouslyheating the air blastdn the wind 1 box, said members extendinginwardly from the adjacent'to, and encircling, a furnace, said furand radially of the furnace,'said plates having their inner radial ends extended through said shell and into the refractory of the said wall and terminated in heat exchange proximity to the interior of the furnace, heat received from the furnace by said inner radial ends of the plates-being transferred by conduction through the plates to within the wind box. I

11. In a furnace having a wind box positioned adjacent to, and encircling, the furnace, said furnace having a wall comprised of a shell and refractory, a plurality of metal plates arranged at intervals around, and disposed longitudinally of,

the wind box and extended radially outwardly from, and radially inwardly of, the shell of said furnace wall, the portion of the plates extending radially outwardly to within the wind box being disfigured from a plane to afford a. greater heating surface in contact with air in the wind box,

the portion of the plates extending radially inwardly of the furnace being disposed in said refractory and positioned 'in proximity to heat in wind box through said shell andinto the refractory. of said wall and ,toward the interior of the furnace to provide afthermal connection between the heat in the furnace and said heating,

- surfaces.

13. In a furnace having a wind box positioned adjacent to, and encircling, the furnace, the wind box and furnace having a. common wall comprised of a shell and a refractory, a plurality of heatconducting plates uniformly distributed around the wind box and disposed vertically in the wind box and radially of the furnace, said plates having their inner radial ends extended through said shell and into the refractory of said wall and terminated in heat exchange relationship with the interior of the furnace, a plurality of fins integral with, and extending from, said plates, respectively, and being disposed in spaced relationship from each other and in proximity to air passing through the wind box, heat reeeived' from the furnace by said inner radial ends being transferred by conduction to the plates and fins within the wind box for heating said air.

14. In a furnace having a wind box positioned adjacent to, and encircling, a furnace, a plurality of metal plates spaced uniformly around the wind box and extending radially outwardlyfrom the furnace into the wind box, each of said plates having spaced fins extended therefrom and dis the wind box and distributed in the wind box by the plates and fins to heat the air passing through the wind box.

15. In a furnace having a wind box positioned adjacent to the wall of the furnace for supplying a blast of air to a plurality of tuyres, said wind box having an inlet adapted to communicate with a source of an air blast and having outlets in communication with said tuyres, a plurality of heat conducting'members extending into said furnace wall andin proximity to the interior of the furnace to receive heat generated within the furnace, said heat conducting members extending radially outwardly from said furnace into the wind box, the portion of the heat conducting,

member having a heat receiving portion formed of material relatively resistant to melting and burning to be mounted adjacent the interior of the furnace, said heat receiving portion forming an elongated head to extend longitudinally of the furnace and forming a segment of a circle of said heads disposable around the annular extent of the furnace. and a heat conducting portion formed of material relatively non-resistant to melting and burning and of relatively high heat conductivity, said heat conducting portion being formed integrally with said heat receiving portion and disposed radially outward from the segment of the circle formed by said heads to extend through the wall of furnace into heat exchange relationship with air exterior of the furnace for heating the said air.

17. The process of pre-heating the air supplied to the tuyres of the furnace from a wind box, comprising: transferring heat, in excess of the amount of heat transferable through the refractory wall of the furnace, from the furnace by metallic conduction through the refractory and thence through the shell of the furnace wall to the wind box, distributing said heat substantially uniformly around the extent of the wind box, and passing the air substantially uniformly around the wind box in proximity to, the conducted heat to supply the air to the tuyres at substantially uniform temperature.

18. The process of pre-heating the air passing through .a wind box to a plurality of tuyres, comprising: guiding the flow of air through the wind box. to substantially equalize the fiow around the extent of the wind box, conducting heat by metallic conduction through the refractory and thence through the shell of the wall 'of the furnace into the wind box substantially uniformly around the extent of the wind box, and uniformly heating the air within the wind box with said conducted heat.

OLIVER SMALLEY. HERBERT A. REECE. 

